Catfish physicals turn up surprising finds

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July 7, 2010 7:51:33 PM PDT

It is check-up time at the California Academy of Sciences in Golden Gate Park where seven giant redtail catfish are due for their annual physical. That may not sound like a big deal, but these are big fish with sharp spines on their fins, and they don't like doctors.

When you plant a live rainforest inside a giant glass dome, you have to be ready for a lot of challenges. The catfish in the tank weigh up to 63 pounds. Some are as long as three and a half feet.

The exhibit is set up so people can stroll above the tank and look down, but sometimes they drop things.

"Glasses, or pacifiers, or shoes, or bottles, all sorts of stuff falls into our tanks," says Laurie Kormos.

Soon after the rainforest opened, Academy staff realized they had a problem.

"We got a radio call that there was a redtail catfish that had some glasses hanging out of his mouth," recalls Kormos.

They called in the vet and discovered glasses were not the only thing the fish had swallowed. So now once a year, the catfish have to have their insides examined.

The operation takes eight people. First divers have to catch the fish. Not easy since the tank is 100,000 gallons, full of nooks and crannies.

"We call it our redtail roundup," says a diver. "For the smaller catfish, we are usually able to sandwich them in between the nets and swim up with them."

The bigger fish are herded to the top where they are scooped up and then carried in stretchers to holding tanks. The water in the tanks is treated with a chemical sort of like Novocain that dentists use on people.

"That will anesthetize them and sedate them," says veterinarian Freeland Dunker who thinks handling redtail catfish can be pretty tricky. "They get big. They are mean."

They also have sharp spines on their fins. So, the team waits until the fish are good and sleepy to begin the exam.

"We do a general physical and that's just a visual on how their skin or scale coat looks, are they good flesh, any wounds," says Dunker.

Then there is the delicate matter of checking the stomach. The smaller fish get a tube slipped down their throat. The tube is lined with aluminum so it reflects. When the vet shines a light in, he can see what's inside.

The tube won't work for the bigger fish, instead the vet has to put his arm in the fish. First he covers up his arm for protection.

"They have what they call forengial teeth in the back of their throat. They have these like sandpaper pads or files," says Dunker.

On the day we visited, none of the fish had anything in their stomach that wasn't supposed to be there. But if you are thinking of putting redtail catfish in your home aquarium, beware. Most of these fish were donated by people who bought them when they were just a few inches long.